In the past several years, paper-based devices have emerged as inexpensive platforms for simple qualitative and semi-quantitative colorimetric assays. See, for example, Li, X. et al., Biomicrofluidics, 2012, 6, 11301. For example, three-dimensional (3D) structures have been developed that allow for the measurement of multiple analytes on a single device. See, for example, Martinez, A. W. et al., Proc Natl Acad Sci 2008, 105, 19606). Recently, devices have been developed that enclose a reaction site with printing toner yielding an assay that is protected from the environment, and is more akin to conventional plastic-based microfluidic devices. See, for example, Schilling K. M. et al., Anal Chem, 2012, 84, 1579. However, this device is complicated in structure, is difficult to use, and requires significant amount of time (>60 min) to construct. In addition, yellow toner is required to be printed over the reaction/detection area to enclose Schilling's device. The yellow colorant may interfere with the chemistries of other reactions, may mask or alter the true color of a result, and thus may render analysis more difficult. Further, the device described by Schilling, et al. does not enable assay expansion with ease; therefore, its utility is limited.
A laminated self-powered, electrochemical device has also been reported by Liu et al. (Angew Chem. Int. Ed., 2012, 51, 1). This device is referred to as an “origami paper analytical device (oPAD),” and is based on a chemical reaction yielding a measurable current as a function of analyte concentration. This device is also complicated to make (includes many steps, layers, and is time consuming), requires folding steps, and requires a four sided process to laminate the structure. In addition, it may take approximately 10 minutes for a sample to fill the device before a measurement can take place for a single analyte. This time period is often too long for time-sensitive diagnostics.